4
Provider Sites  Prepare a digital collection so that it is web accessible to the preservation nodes  Expose a “manifest” web page for each collection, according to LOCKSS specifications. Grants permission for LOCKSS to crawl Gives starting point for crawl  Provide information sufficient to create a LOCKSS plugin for the collection (or else create the plugin themselves and reposit that plugin with the LOCKSS network)

5
LOCKSS Peer Nodes  Data caches for harvested content  Caches organized into archival units (AUs)  Nodes can select which AUs to crawl and preserve  There must be >= 6 copies of an AU in order for the polling process to work properly

6
Plugins / Plugin Repository  Tell LOCKSS where, how and how often to crawl a provider site for AUs  Plugins are Java based  Distinct from core LOCKSS software

7
Cache Manager  Distributed separately from LOCKSS  Can remotely inspect and manage the caches on the various peer nodes

8
Title / Conspectus Databases  Title database on each node describes and manages which AUs to preserve on that node  Conspectus Database designed for MetaArchive Project, provides more extensive metadata about the preserved digital collections, and feeds the Title database with entries

12
Polling Refresh Timer  A peer sets a refresh timer for a given AU to determine the interval between successive polls  System parameter R is the mean for the possible random values generated for the refresh timer

14
Polling Outcome – ‘Landslide Win’  The poller considers its current copy to have integrity  This is the only scenario in which an opinion poll concludes successfully  The poller updates its reference list and then waits until the next polling period (determined by the refresh timer)

15
Reference List Update  Happens only after a successful poll  Poller removes the inner circle peers who had valid votes in the last opinion poll  Culls peers it has not been able to contact for some time  Adds outer circle peers whose votes were valid and eventually agreeing